Believe it or not

By David Catchpoole

How plants ‘know’ when to make sunscreen


Plants harvest light energy from sunlight (a process known as photosynthesis1) but the UV-B wavelengths of sunlight are potentially damaging to them (just as they are to us). Scientists have known for decades that plants make their own sunscreen chemicals for the outer tissues of leaves when UV-B reaches damaging levels. But they didn't know how plants could recognise when it was necessary to switch on sunblock production.

Now researchers have found that plants have a special photoreceptor to detect UV-B light and then switch on the changes in gene expression needed to produce the plant's sunscreen.2

The sunblock chemicals are deposited in the leaf tissues exposed to the bright sunlight and absorb UV-B, protecting the leaf cells below.

At the same time, exposure to UV-B stimulates production of enzymes that repair any damage to DNA, prevent oxidative damage to cells, and keep the photosynthetic machinery in good working order.

A chance arrangement? No—rather, it speaks powerfully of the practical handiwork of the Creator.

1. See

2. Experts reveal why plants don't get sunburn, University of Glasgow news,, 30 March 2011.

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